Apparatus for controlling blade positioning in a cutter head assembly

ABSTRACT

Apparatus for controlling operative positioning of individual blades in a cutter head assembly of a type which may be used for cutting &#39;&#39;&#39;&#39;blind&#39;&#39;&#39;&#39; arcuate slots in a workpiece, such as the seal slots required for rotors of rotary, combustion engines. A plurality of blade-holding structures, and their associated blades, is positioned about a circumference of the cutter head. Each blade-holding structure is mounted so as to be independently movable axially relative to the cutter head to thereby provide for successive and progressive engagement and disengagement of individual blades with the workpiece as the cutter head rotates during a cutting operation. A portion of each blade-holding means is carried within a fluid chamber which communicates with a fluid pressure system so as to normally urge each blade-holding structure toward its cutting position. In addition, a stop limit means is contained in the fluid chamber to limit the movement of each blade-holding means in a cutting direction. Each stop limit means is arranged to create a dash pot effect with fluid contained in the chamber during final increments of movement of the blade-holding means to its extended limit position. This arrangement reduces shock and vibration in the cutter head assembly and minimizes noise during operation of the assembly. Also, the dash pot effect eliminates any tendency for the bladeholding structure to bounce as it moves very rapidly to its limit position for cutting a slot.

United States Patent [1 1 Hunkeler Dec. 11, 1973 APPARATUS FOR CONTROLLING BLADE POSITIONING IN A CUTTER HEAD ASSEMBLY Ernst J. Hunkeler, Fairport, N.Y.

[73] Assignee: The Gleason Works, Rochester,

22 Filed: July 31,1972

21 Appl. No.: 276,620

[75] Inventor:

[52] US. Cl 408/54, 90/30, 90/31 [51] Int. Cl..... B23b 41/12, B23b 47/18, B23d 5/02 [58] Field of Search 90/30, 31; 408/54 [56] References Cited UNITED STATES PATENTS 3,143,923 8/1964 Krzyszczuk 408/54 FOREIGN PATENTS OR APPLICATIONS 1,269,455 5/l968 Germany 408/54 Primary Examiner-Francis S. I-Iusar Attorney-Morton A. Polster et al.

[57] ABSTRACT Apparatus for controlling operative positioning of individual blades in a cutter head assembly of a type which may be used for cutting blind arcuate slots in a workpiece, such as the seal slots required for rotors of rotary, combustion engines. A plurality of bladeholding structures, and their associated blades, is positioned about a circumference of the cutter head. Each blade-holding structure is mounted so as to be independently movable axially relative to the cutter head to thereby provide for successive and progressive engagement and disengagement of individual blades with the workpiece as the cutter head rotates during a cutting operation. A portion of each blade-holding means is carried within a fluid chamber which communicates with a fluid pressure system so as to normally urge each blade-holding structure toward its cutting position. In addition, a stop limit means is contained in the fluid chamber to limit the movement of each bladeholding means in a cutting direction. Each stop limit means is arranged to create a dash pot effect with fluid contained in the chamber during final increments of movement of the blade-holding means to its ex tended limit position. This arrangement reduces shock and vibration in the cutter head assembly and minimizes noise during operation of the assembly. Also, the dash pot effect eliminates any tendency for the blade-holding structure to bounce as it moves very rapidly to its limit position for cutting a slot.

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APPARATUS FOR CONTROLLING BLADE POSITIONING INA CUTTER HEAD ASSEMBLY RELATED APPLICATION This application is related to the subject matter of a co-pending application filed by Ernst J. I-Iunkeler on May 22, 1972 under Ser. No. 255,853, entitled Method and Apparatus for Cutting BlindSlotsf and owned by the assignee of this application.

BACKGROUND OF INVENTION As discussed intheabove-identified co-pending application, it is necessary to form so-called blind" slots in certain types of workpiece manufacture, i.e., slots which do not continue along a surface of a workpiece to at least one of its edges. The above-mentioned copending application describes method and apparatus for cutting such blind slots in a workpiece by using a continuously rotating cutter head carrying a plurality of individual blades positioned ina face of the cutter head at equal angular spacings on a radius chosen according to the are desired for the slot to be cut. Each individual cutter blade is controlled to extend axially, relative to the face surface of the cutter head, so as to be independently movable relative to a workpiece along an axis which brings the blade into and out of cutting engagement with the workpiece during operation of the machine. Individual cutter blades are supported by separate blade-holding means controlled to extend and retract the blades to their cutting positions.

The aforesaid application also describes a hydraulic control system for controlling positioning of individual blades in a cutter head. In this system, each blade is constantly biased toward its extended, cutting position through the force of hydraulic fluid applying a pressure to a piston associated with a blade-holding means for each blade. In addition, cam means are carried by a part of the apparatus for engaging each bladeholding means to move its associated blade out of engagement with a workpiece in accordancewith a sequence ofoperation of the machine.

For a more detailed discussion of the type of apparatus with which the present invention is concerned, reference is made to the above-identified, co-pending application which is incorporated herein by reference to the extent necessary to provide a background understanding of the present invention.

SUMMARY OF INVENTION The present invention is concerned with specific improvements in means for controlling the positioning and operation of a plurality of movable blade means of the type discussed above. More specifically, the present invention provides for a fluid pressure control means which normally biases each cutting blade into a cutting position and which includes means for stopping movement of each blade in its cutting limit position in a way in which shock, vibration and noise are reduced in the machine.

In thetype of operation contemplated for machines having a cutter head'carrying a plurality of movable blade means, it is essential that each blade means of the plurality be moved into and out of its cutting position in accordance with a precise sequence of operation for the machine. This is especially important in the cutting of blind slots wherein working parameters are very confined and in which position and depth of cut must be very precisely controlled.

In accordance with the present invention, a fluid pressure means, such as a hydrulic control circuit, is arranged to normally urge each blade means of a cutter head assembly in a cutting direction. This is accomplished by mounting each blade means in an associated blade-holding structure carried within the cutter head assembly for movement along an axis which brings the blade means into and out of cutting engagement with a workpiece during operation of the machine. The fluid pressure means includes a fluid chamber associated with each blade-holding structure so that pressure of fluid within the chamber can be applied to a portion of the blade-holding structure which is received within, or in communication with, the chamber. The arrangement is such that fluid pressure normally urges the bladeholding structure in a cutting direction.

The fluid pressure means of the present invention further includes a stop limit device associated with each blade-holding structure for stopping movement of the blade-holding structure at a limit position in its cutting direction. In a preferred embodiment, the stop limit means comprises an element contained within the fluid chamber and having a bore therethrough for receiving passage of a terminal end portion of the bladeholding structure. The terminal end portion of the blade-holding structureis provided with an enlarged head element for contacting the stop limit means. The

I enlarged head element and stop limit means are related to. one another in such a way as to produce a dash pot effect as the enlarged head element is moved rapidly to its limit position against the stop limit means. This effect is obtained with the same hydraulic fluid, contained within the fluid chamber, which causes the blade-holding structure to be moved to its cutting position. As a result of this arrangement, there is a dampening of final increments of movement of each bladeholding structure during movement to its limit cutting position. This prevents a sharp impact between the blade-holding structure and its limit means, thereby reducing shock and vibration and minimizing noise. in the ent invention will be discussed more completely in the detailed discussion which follows. In that discussion reference will be made to the accompanying drawings as briefly described below.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an elevational view of a type of machine in which the apparatus of the present invention may be utilized;

FIG. 2 is a top plan view of the machine of FIG. 1;

FIG. 3 is an elevational view, partly in section, of a cutter head assembly of the type contemplated by the present invention;

FIG. 4 is an isometricview of a portion of a cutter head assembly, showing basic relationships between a blade-holding means and a cam means associated with the assembly;

FIG. 5 is an elevational view in enlarged scale, and in section, of a portion of the cutter head assembly shown in FIG. 3;

FIG. 6 is an elevational view of a blade-holding means, drawn in the same scale as FIG. 5 and as would be seen on line 4--4 of FIG. 5;

FIG. 7 is a top plan view ofa sector of the cutter head assembly shown in FIG. 5, drawn in the same scale as FIG. 5;

FIG. 8 is a top plan view, in section, of portions of the cutter head assembly of FIG. 5, as seen on line 6-6 thereof; and

FIG. 9 is a schematic view showing basic relationships of a series of individual blade means and a control circuit for a machine utilizing the concepts of the present invention.

DETAILED DESCRIPTION OF DISCLOSURE Referring to FIGS. 1 and 2, the improved apparatus of the present invention is illustrated in use with a machine designed to cut blind-ended, arcuate slots in flat face surfaces of a rotor for a rotary combustion engine. The machine includes a frame 10 which carries a tool head 12 and a workhead 14, each mounted on appropriate sides 16 and 18, respectively, for relative adjustment thereon. The tool head 12 carries a spindle housing 20 in which a spindle 22 is mounted for rotation about an axis 24. Spindle 22 is rotated by a drive motor 26 in a manner known in the art. Spindle 22 is also movable axially so as to provide a feed motion for a cutter head carried thereby.

The work head 14 carries a rotatable work support 28 which includes suitable means (not shown) for clamping and positioning the workpiece 30 relative to the spindle 22. The workpiece 30 can be considered to be a typical delta-shaped rotor for a rotary combustion engine, although the principles of this invention can be applied to other work applications as well.

Connected to the end of the spindle 22 is a cutter head 32, shown in greater detail in FIG. 3. The cutter head 32 is secured to a face of the spindle 22 by bolts or other fastening devices in a manner known in this art. The cutter head functions to support and carry a plurality of blade means, which will be discussed in greater detail below, so that the blade means can be brought into engagement with the workpiece 30 while the cutter head is rotating on its axis 24 and during feeding movement of the cutter head toward the workpiece.

Feeding movement of the spindle 22 is controlled in a manner known in this art and shown only schematically in FIG. I. A spring means (not shown) biases the spindle 22 against one side of a lever 34 pivotally mounted at its one end to a shaft 36. A cam follower 38 attached to an opposite end of the lever 34 engages a control cam 40. In one embodiment of the machine, the cam 40 is designed so that spindle 22 is caused (a) to move gradually in an axial direction toward workpiece30 to provide the desired infeed of the cutter head, (b) to dwell at its full depth position to assure that the entire slot has been cut to full depth, and then (c) to move rapidly in the opposite axial direction to withdraw the cutter head and its plurality of blades out of engagement with the workpiece, following completion of the cutting cycle.

Referring to FIG. 3, the cutter head assembly is illustrated, partly in cross section, as it would appear when bolted to the end of the spindle 22. The cutter head includes a main body, assembled from a number of components, which is adapted to be bolted to an end face of spindle 22 with a number of bolt means 42, as is well known in this art. The main body of the cutter. head rotates with the spindle and carries with it a plurality of blade elements 44 which function as cutting tools when brought into engagement with a workpiece. Associated with the cutter head assembly of FIG. 3 is a housing component 46 which moves axially with spindle 22 but is restrained from rotation therewith by a pin and roller 45 fixed to spindle housing 20, the pin and roller 45 moving relative to housing component 46 in slide 47 during axial movements of spindle 22.

FIGS. 4-8 illustrate details of the cutter head and an individual blade-holding means associated with one of the blades 44. Generally, each blade holding means comprises an elongated structure 48 which is mounted in the cutter head so as to be movable back and forth along its longitudinal axis. Each blade-holding means 48 carries the blade element 44 at a terminal end portion which projects outwardly beyond a face of the cutter head, and thus, axial movement of the bladeholding means provides for a corresponding movement of the blade element toward and away from a workpiece. Each blade-holding means 48 is independently controlled, in a manner to be described below, to provide for a controlled movement of each blade 44 into and out of correct positions for cutting a blindslot at whatever depth of cut is determined by the axial feed position of the spindle 22. Basically, each bladeholding means 48 is urged toward an extended, cutting position by an application of fluid pressure to a portion of the blade-holding means contained within the cutter head, and retraction of each blade-holding means is effected with the use of separate cams 50 carried in space positions about a circumference within the stationary housing 46 so as to provide for a periodic retraction of each blade holding means 48 as its follower 52 engages and follows the cam. Such a basic arrangement is known from said above-identified application and does not constitute the present invention.

Referring to the details of FIG. 5, it can be seen that each blade-holding means 48 is fitted within a passageway formed into the cutter head 32 so as to be movable along its longitudinal axis for limited extension and'retraction movements. As viewed in FIG. 5, a lower terminal end of the blade-holding means 48 carries a blade 44, and an upper terminal end of the bladeholding means 48 is received within fluid chamber 54 formed in a portion of the cutter head assembly. A lower body portion of the blade-holding means 48 is mounted between bearing elements 56 which are contained in bearing cages for contacting radially inward and outward flat surfaces 58 and 60, respectively, of the blade-holding means 48. This arrangment provides for limited radial adjustment of each blade-holding means 48 against the positions of the bearings on its up posite surfaces 58 and 60 while also providing for a rolling engagement of the surfaces 58 and 60 with portions of the cutter head. The bearing cage fitted against the surface 60 is preferably spring-loaded with Belleville washers 62 so as to normally urge the bladeholding means 48 radially inwardly to its set position in the cutter head. A shim means 64 is inserted between the bearing cage for the surface 58 of the blade-holding means and the main body of the cutter head so as to provide for very precise adjustment of position of the blade-holding means by proper selection of the shim 64.

An upper body portion of the blade-holding means 48 is cut out so as to place the cam follower 52 more or less over the central longitudinal axis of the bladeholding means. This placement minimizes unwanted deflections which otherwise may be applied to the elongated body of the blade-holding means when the cam follower 52 makes contact with a cam 50. The cam follower 52 comprises a roller element of known design mounted to the blade-holding means 48 with a pin 66.

The uppermost end of each blade-holding means, as viewed in the FIG. 5 orientation, is received into the fluid chamber 54 so that a downward force can be applied to the blade-holding means, and its associated blade, with hydraulic fluid carried under a positive pressure in the fluid chamber 54. The fluid chamber 54 preferably comprises a continuous annular chamber extending around the cutter head so as to intersect, or communicate with, each of the blade-holding means, or it may alternatively comprise a series of separate chambers in fluid communication with each other and with each blade-holding means. As shown in FIG. 5, the upper terminal end of the blade-holding means 52 is provided with an end cap 68 which is bolted to the terminal end of the blade-holding means with a bolt 70. The upper surface areas of the end cap 68 and the exposed head of the bolt 70 are greater in total area than the surface area beneath the end cap 68, and therefore, the blade-holding means is normally urged downwardly to its most extended position as shown in FIG. 5. In this position, the end cap 68 contacts, and is limited in its further movement, by a stop limit means 72 in the form of a block element having a bore therethrough for allowing passage of the upper terminal end of the bladeholding means 48. The stop limit means 72 determines the full extended position for each blade-holding means and its associated blade inasmuch as there is no loadbearing contact (or no contact at all, if desired) between the cam follower 52 and the cam 50 except during times when the blade-holding means is to be retracted against the pressure of the hydraulic fluid contained in the fluid chamber 54. The stop limit means 72 also functions to seal the fluid chamber 54 at the point where the blade-holding means passes through the bottom of the chamber.

The stop limit means 72 is secured to a bottom surface of the annular chamber 54 by suitable means, such as bolts 74 (see. FIGS. 6 and 7) so as to establish a sealed relationship between the stop limit means 72 and the bottom of the fluid chamber. A sealing ring 76 may be included in a ring groove formed in a bottom face of the stop limit means, however, the sealing ring is not an essential part of the assembly. A bore having a circular cross section is provided through the stop limit means 72 to allow passage of the cylindrical upper end of the blade-holding means 48. Sufficient clearance between the upper end of the blade-holding means and the stop limit means is provided to allow for relative sliding movement between the two elements, and a small amount of hydraulic fluid is permitted to leak from the fluid chamber 54 past the upper cylindrical end of the blade-holding means 48 to provide lubrication of the upper end of the assembly.

When the blade-holding means is moved downwardly to the position shown in FIG. 5 (as would be the case when its follower 52 drops downwardly from the end of a cam 50 to a point of no load-bearing contact with any cam element), the end cap 68 of the blade-holding means tends to squeeze or trap a quantity of hydraulic fluid between its bottom surface and the upper surface of the stop limit means 72. This action results in a dash pot effect which dampens the final increment of movement of the blade-holding means to its stop limit position, and the result of this effect is to reduce shock, vibration and noise in the operation of the cutter head. In order to prevent freezing or binding contact between the end cap 68 and the stop limit means 72, the end cap is provided with only sufficient surface area to effectively stop the blade-holding means at a precise level without creating a large area of surface contact between the end cap and the stop limit means.

As previously discussed, individual blade elements 44 are mounted at lower terminal ends of the bladeholding means 48. Referring to FIGS. 5 and 8, it can be seen that each bladeholding element is secured between a flat surface 80 of the blade-holding means and a tool holder block 82 which is fitted around three sides of the lower terminal end of the blade-holding means. A tool holder clamp 84 is fitted across the remaining side of the terminal end of the blade-holding means and includes outwardly extending flanges 86 for being re ceived in corresponding channels formed in the tool holder block 82; A screw device 88 provides for final tightening of the blade-holding components to establish a firm seating of the blade 44 in. its desired position. The channels 86 of the tool holder block may be shaped to draw the channeled portions of the tool holder block toward the clamp member 84 as the screw 88 is tightened. I I 7 FIGS. 5 and 6 also illustrate a conduit 90 which extends from a source of supply of compressed air (not shown) to the lower terminal end portion of 'the blade holding means so that compressed air can be supplied to the seating area of the blade-holding means when blades are changed in the cutter headQThe lower end of the conduit 90 is blocked with a screw insert 91, and an intersecting conduit is provided above the blocked area so that air can exhaust at the points 92 and 93 (see FIG. 5) to provide a cleansing action of the blade seating area and surfaces of the tool holder block 82 and clamp 84 during removal and replacement of blades in the cutter head assembly.

Having described structural features of the present invention, it can be appreciated that all component parts of the cutter head assembly are to be manufactured in accordance with known techniques and known materials which meet design requirements of the machine. The blade-holding means and control system discussed above provide for extremely precise fitting of a plurality of blades within a cutter head assembly. For example, the radius position of each blade-holding means can be held within 0.0002 inches and the depth position of each blade can be held within 0.0005 inches with the structures discussed above. The various components discussed above may be modified to provide further convenience in assembly and disassembly of component parts, and an example of such a modification would be to provide for spring detents between the tool holder block 82, its clamp 84, and the terminal end of the blade-holding means to which these parts are to be assembled. Each blade element 44 may be of any re quired design for the type of cutting to be achieved. For

example, each blade may be lapped or honed on one side only to provide relief on that side of the blade, and an effective relief may be provided on an opposite side of the blade by forming the surface 80 of the bladeholding means at a slight angle which orients the cutting face of each blade element to a required position.

The cutter head assembly which has been discussed above is especially useful for cutting blind slots in rotor blocks for rotary combustion engines by the method and with the type of apparatus described in the aforesaid co-pending application. FIG. 9 schematically illustrates a typical relationship between a plurality of blade-holding means 48 and the type of hydraulic control system which has been discussed above. Each blade-holding means 48 is biased at all times towards its extended position by fluid pressure applied to an upper terminal end (illustrated as a piston) of the blade-holding means. Fluid pressure is supplied to separate fluid chambers associated with the separate blade-holding means, as schematically illustrated, or may be supplied to a single continuous chamber intersecting upper terminal ends of all blade-holding means as shown in FIGS. and 7. Hydraulic fluid is pumped from a reservoir 100 by a pump 102 and is delivered under pressure to the control circuit for the cutter head assembly. In the arrangement of FIG. 9, a cam track 50 is provided about the entire cutter head assembly so that follower elements 52 of each blade-holding means 48 are in continuous contact with the cam track. However, the cam surfaces 50 may comprise separate sections which function only to lift individual bladeholding means at appropriate times, as discussed above with reference to FIGS. 1-8.

In considering the arrangement of FIG. 9, assume that the cutter head 32 is rotating in the direction of the arrow shown in the drawing, thereby carrying with it the plurality of blade-holding means 48 whose cam followers 52 roll along the surface of the cam track 50. As each cam follower 52 reaches the first cam ramp 104, it is first driven upwardly by the inclined surface 106, and then, shortly thereafter, it moves down to its cutting position when it reaches the bottom of the inclined surface 108. Similar movements occur when individual blade-holding means 48 move up and down over the successive cam ramp 110 having inclined surfaces 112 and 114.

Thus, as each follower 52 arrives at inclined surfaces 108 and 114, its associated blade-holding means is suddenly extended to its limit cutting position, and correspondingly, when each follower 52 arrives at inclined surfaces 106 and 112, its associated blade-holding means is withdrawn to its non-cutting position. The cam ramp units 104 and 110 are so designed that the difference between the extended and retracted positions of each blade-holding means is greater than the depth of the slots being cut. Also, the slopes of the inclined surfaces are designed to permit each blade element 44 to move axially a distance equivalent to the full depth of the slot in less than it takes a blade to cross an access hold 116 or 118 formed at each end of the workpiece where the slot is to be formed. In this way, each successive blade pops into the access hole 116 to being its cutting engagement with the workpiece 30, and then withdraws at the instant it reaches access hold 118. It should be noted that the slope of the inclined surface 108 of cam ramp 104 must necessarily be steeper than the slop of the inclined surface 112 of the cam ramp since the retracting blade can be raised as soon as its leading edge has entered access hole 118, using the full width of the access hole 118 during such retraction, while the extending blade cannot be moved to its full-depth cutting position until such time as its trailing edges have cleared the leading edge of access hole 116.

A special design of the arrangement shown in FIG. 9 provides for rapid response in the hydraulic control system associated with each of the blade-holding means 48. Referring to the cam ramp 110, its inclined surfaces 112 and 114 are designed to be exactly the same length and are positioned relative to each other at a distance substantially equal to the spacing between each successive blade.

Therefore, at the exact instant that the follower 52c arrives at the beginning of the inclined surface 112, the upper terminal end of the blade-holding means 48b begins to increase the volume of liquid in its associated fluid chamber 54b. Accordingly, it is not necessary for the upper end of the blade holding 48c to push a long column of fluid through the hydraulic circuit and back to the pump 102. Instead, the fluid being moved out of the fluid chamber 54c can move immediately into the nearby chamber 54b, thereby greatly increasing the response time of the hydraulic system.

The cam ramp 104 operates on the same general principle as that described for the cam ramp 110 to provide for balancing of hydraulic fluid between adjacent fluid chambers and to increase response time. However, the cam ramp 104 differs somewhat from the cam ramp 110 in that its inclined surface 108 is steeper and shorter than its surface 106. The steepness of the inclined surface 108 is, as noted above, dictated by the size of the access hole 116 and by the width and expected maximum angular velocity of each cutter blade 44. On the other hand, the inclined ramp 106 can be less steep, and this is particularly desirable in order to save wear on the cam followers 52. The slightly greater inclined surface 106, as compared to the inclined surface 108, provides an added advantage of creating a slight surge of hydraulic pressure applied to the upper end of the blade-holding means 48c at the time it reaches its fully extended position, and this overcomes any tendency for the blade-holding means to bounce whenit gaches its extended limit position.

7' Although (Heather/e invention has been described with reference to certain specific and preferred embodiments, it will be understood by those skilled in this art that equivalent and substitute changes can be made in the described structures to achieve the same benefits and results of the concepts of the present invention. Such equivalent and substitute changes are intended to be included within the scope of protection defined in the claims which follow.

What is claimed is:

1. Apparatus for use with a machine which includes a cutter head means for carrying a plurality of blade means in spaced positions about a circumference of the cutter head means so that individual blade means can be brought into successive and progressive engagement with a workpiece to form a blind slot in the workpiece, said apparatus being characterized by a separate blade-holding means for holding each blade means of said plurality of blade means, and each blade-holding means being mounted in said cutter head so as to be independently movable relative to said workpiece along an axis which moves an associated blade means into and out of cutting engagement with the workpiece during operation of the machine,

fluid pressure means for urging each blade-holding means in a cutting direction so as to movean associated blade means into cutting engagement with said workpiece in accordance with a sequence of operation for the machine, said fluid pressure means including means defining a fluid chamber which communicates with a portion of a bladeholding means to apply a pressure on said portion to thereby urge the blade-holding means in said cutting direction, and

stop limit means contained in said fluid chamber for stopping movement of each of said blade holding means at a limit position in said cutting direction, said stop limit means and said portion of each blade-holding means being arranged to create a dash pot effect with fluid contained in said chamber during final increments of movement of the blade-holding means to said limit position.

2. Apparatus according to claim 1 wherein said portion of said blade-holding means comprises a terminal end portion of the blade-holding means, said terminal end portion being received into said fluid chamber for limited movement along its axis within the fluid chamber, and said fluid chamber being formed within assemblies associated with said cutter head.

3. Apparatus according to claim 2 wherein said terminal end portion includes an enlarged head element for contacting said stop limit means.

4. Apparatus according to claim 3 wherein said stop limit means includes a bore therethrough for passage of said terminal end portion.

5. Apparatus according to claim 1 wherein said fluid chamber intersects a central longitudinal axis of said blade-holding means to thereby minimize deflection of the blade-holding means when a force of fluid pressure is applied thereto.

6. Apparatus according to claim 1 and including:

cam means carried by said machine for engaging each of said blade-holding means to move an associated blade means out of engagement with a workpiece in accordance with said sequence of operation for the machine.

7. Apparatus according to claim 6 and including:

cam follower means carried by each of said bladeholding means for engaging said cam means, said cam follower means being positioned near a central longitudinal axis of the blade-holding means to minimize deflection of the blade-holding means during engagement of the cam follower means with said cam means.

8. Apparatus according to claim 1 wherein said blade means are arranged in equally spaced positions about a circumference defined on a face of the cutter head.

9. Apparatus according to claim 1 wherein each of said blade-holding means comprises an elongated member having means for carrying a blade means at one end thereof, and including bearing means for mounting said elongated member in said cutter head for movement along its central longitudinal axis into and out of cutting engagement with a workpiece during operation of the machine.

10. Apparatus according to claim 9 and including means for radially adjusting the positions of said bladeholding means relative to said cutter head.

11. Apparatus according to claim 1 wherein said fluid chamber comprises a single annular chamber formed in said cutter head means so as to communicate with all of the blade-holding means mounted in the cutter head.

12. Apparatus according to claim 11 wherein said fluid chamber is connected to a source of hydraulic fluid for filling the chamber and for maintaining a positive pressure against all of said blade-holding means. 

1. Apparatus for use with a machine which includes a cutter head means for carrying a plurality of blade means in spaced positions about a circumference of the cutter head means so that individual blade means can be brought into successive and progressive engagement with a workpiece to form a blind slot in the workpiece, said apparatus being characterized by a separate blade-holding means for holding each blade means of said plurality of blade means, and each blade-holding means being mounted in said cutter head so as to be independently movable relative to said workpiece along an axis which moves an associated blade means into and out of cutting engagement with the workpiece during operation of the machine, fluid pressure means for urging each blade-holding means in a cutting direction so as to move an associated blade means into cutting engagement with said workpiece in accordance with a sequence of operation for the machine, said fluid pressure means including means defining a fluid chamber which communicates with a portion of a blade-holding means to apply a pressure on said portion to thereby urge the blade-holding means in said cutting direction, and stop limit means contained in said fluid chamber for stopping movement of each of said blade holding means at a limit position in said cutting direction, said stop limit means and said portion of each blade-holding means being arranged to create a dash pot effect with fluid contained in said chamber during final increments of movement of the blade-holding means to said limit position.
 2. Apparatus according to claim 1 wherein said portion of said blade-holding means comprises a terminal end portion of the blade-holding means, said terminal end portion being received into said fluid chamber for limited movement along its axis within the fluid chamber, and said fluid chamber being formed within assemblies associated with said cutter head.
 3. Apparatus according to claim 2 wherein said terminal end portion includes an enlarged head element for contacting said stop limit means.
 4. Apparatus according to claim 3 wherein said stop limit means includes a bore therethrough for passage of said terminal end portion.
 5. Apparatus according to claim 1 wherein said fluid chamber intersects a central longitudinal axis of said blade-holding means to thereby minimize deflection of the blade-holding means when a force of fluid pressure is applied thereto.
 6. Apparatus according to claim 1 and including: cam means carried by said machine for engaging each of said blade-holding means to move an associated blade means out of engagement with a workpiece in accordance with said sequence of operation for the machine.
 7. Apparatus according to claim 6 and including: cam follower means carried by each of said blade-holding means for engaging said cam means, said cam follower means being positioned near a central longitudinal axis of the blade-holding means to minimize deflection of the blade-holding means during engagement of the cam follower means with said cam means.
 8. Apparatus according to claim 1 wherein said blade means are arranged in equally spaced positions about a circumference defined on a face of the cutter head.
 9. Apparatus according to claim 1 wherein each of said blade-holding means comprises an elongated member having means for carryIng a blade means at one end thereof, and including bearing means for mounting said elongated member in said cutter head for movement along its central longitudinal axis into and out of cutting engagement with a workpiece during operation of the machine.
 10. Apparatus according to claim 9 and including means for radially adjusting the positions of said blade-holding means relative to said cutter head.
 11. Apparatus according to claim 1 wherein said fluid chamber comprises a single annular chamber formed in said cutter head means so as to communicate with all of the blade-holding means mounted in the cutter head.
 12. Apparatus according to claim 11 wherein said fluid chamber is connected to a source of hydraulic fluid for filling the chamber and for maintaining a positive pressure against all of said blade-holding means. 